We switch gears now to Iraq which took several new steps toward the abyss. The blood thirty band of fundamentalists believed to have captured another small town while neighboring Iran has reportedly sent in two thousand of its troops. A U.S. Air carrier arrived in the persian gulf as president Obama weighs military intervention. It is a tinder box, and ABC's chief foreign correspondent terry Moran is on the ground in Iraq. Reporter: These are good days for the jihadists in Iraq. While the momentum of their lightning advance has slowed, it has not stopped, and they celebrate here in a video they posted online that can't be independently verified. But Isis is coming. As the fighters of the islamic state of Iraq and Syria are known, and Baghdad is bracing for attack. Heavy security has been deployed throughout the capital, and another sign of the tense times here? Young men taking up arms, keen for battle. But these are shia volunteers. They form one piece of Iraq's shattered mosaic of community. Shia dominate the south. Sunni the west and center, kurds the north. The Isis forces are mostly Sunni. They hate the shia dominated government in Baghdad which is B backed by Iraq and Syria. So the fight against Isis is becoming a sectarian civil war that could split the country and drag the U.S. Into a strange cooperation with sworn enemies in Tehran, all to save Iraq. For many, their home, their country, is already lost. U.n. Officials visited a new refugee camp today. Hundreds of thousands have nowhere to go. They need tents, electricity, clean water, food, health. These are the basic things that for this piod of time they need. Reporter: Tonight there are reports that those Iranian troops have already arrived here to join the fight. About 2,000 of them. With the U.S. War ships steaming into the persian gulf and president Obama weighing his options, the crises here in Iraq is spreading rapidly.

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